High voltage bushing



E. D. EBY

HIGH VOLTAGE BUSHING Filed Sept. 15, 1936 Feb. 22, 1938.

Inventor" Eugene D. 13b9, b #0924; A". H His Attorney nil-um Mil -ii Unmun g /4 Patented Feb. 22, 1938 PATENT OFFICE HIGH VOLTAGE BUSHING Eugene D. Eby, Pittsfield, Mass,

assignor to General Electric Company, a corporation of New York Application September 15, 1936, Serial No. 100,871

3 Claims.

My invention relates to high voltage bushings of the type which includes a liquid dielectric such as a specially prepared insulating oil. The liquid dielectric is subject to deterioration by 5 moisture and oxidation if the air around the bushing reaches the liquid. The general object of the present invention is to provide an improved bushing structure, including a liquid dielectric, and so arranged asto exclude all outside air and 10 thus protect the liquid from contamination.

The invention will be better understood from the following description taken in connection with the accompanying drawing in which Fig. 1 is a perspective view of a bushing constructed 15 in accordance with the invention, and Fig. 2 is a view, partly in section, of the upper or outer end of the bushing.

Like reference characters indicate similar parts in both figures of the drawing. 20 The bushing shown in the drawing includes tubular end sections I and II formed of suitable insulating material such as porcelain. These insulating sections l0 and II are joined by an intermediate tubular section l2 formed of metal and provided with a flange l3 for supporting the bushing through an opening in the casing of a transformer or other electrical apparatus. The sections III, II, and I2 of the bushing form an outer wall or casing which surrounds an axial 30 tubular conductor H. The space around this tubular conductor is filled, in part at least, with an insulating liquid l5, such as a specially prepared oil having high dielectric strength. In

order to permit expansion and contraction of the 35 liquid IS in response to changes in temperature,

the bushing is provided with an expansion chamber l6 having a base plate I! bolted to a clamping ring l8 cemented around the upper or outer end of the section I 0 of the bushing. A glass 40 cylinder I9 is secured between the base plate I1 and a cover or cap 20 of the expansion chamber, suitable gaskets 2| and 22 being provided to seal the joints between the glass cylinder and the cap and base of the expansion chamber.

45 Spring washers 23 between the base I! and the nut 24 threaded onto the conductor II assure a tight assembly of parts while permitting a difference in the thermal expansions of the conductor l4 and the outer wall of the bushing.

50 The liquid l extends into the expansion chamber l6 to permit thermal expansion and contraction of the liquid, and at the same time to keep all spaces within the wall of the bushing completely filled with liquid.

55 The cap 20 of the expansion chamber includes an annular top portion 25 with flanges 26 and 21 extending from its inner and outer edges respectively. The lower edge of the outer flange 21 is inturned and is formed with a groove for the gasket 2|. The inner flange 26 surrounds the conductor H from which it is spaced to accommodate a spring 26 and a seal 28. A ring 29 has an inner portion threaded onto the tubular conductor l4 and formed with a groove fltting tightly over the upper edge of the seal 28. The outer portion of the ring 29 is formed with a groove for a gasket 30 between this ring 29 and a narrow rim formed on the upper surface of the cap 20. The spring 26 is compressed between the seal 28 and a shoulder formed by the inturned lower edge of the flange 26 of the cap. A washer 28 distributes the pressure of the spring uniformly along the surface of the seal 28. The seal 28 fits tightly between the conductor l4 and the flange 26, the inner surface of the flange 26 being approximately cylindrical and smooth to permit sliding engagement with the seal. The seal 28 is also preferably formed of some suitable rubber-like or other elastic material so that it will be spread tightly between the conductor l4 and the flange 26 by the pressure of the spring 26. The spring 26' also forces the cap 26 toward the wall IQ of the expansion chamber and maintains tight joints at the gaskets 2| and 22. Any relative motion between the conductor l4 and the wall of the bushing will cause relative motion between the seal 28 which is secured to the conductor [4 and the flange 26 of the cap 20, the seal 28 merely sliding along the inner smooth surface of the flange 26. A second ring 3| threaded onto the upper end of the conductor I4 is sealed to the ring 29 by a gasket 32 and secured by a pin 33 to a terminal 34 brazed or soldered to the strands of. the stranded conductor 35 extending through the tubular conductor 14 and providing additional conductivity between the terminals of the bushing. A terminal cap 36 threaded onto the outer end of the terminal 34 is sealed to the ring 3| by a gasket 31.

The construction which has been described effectively excludes all outside air and moisture and protects the liquid I5 from contamination, the seal at the same time permitting relative 50 movements of parts due to thermal expansion without undue stresses on any of the parts. It is obvious that any leakage of air or moisture passing the gaskets 30, 32, or 31 or through the threaded joint between the ring 3| and the tubular conductor I! cannot pass the seal 28 and reach the liquid IS.

The invention has been explained by describing and illustrating a particular form thereof, but it will be apparent that changes may be made without departing from the spirit of the invention and the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. A liquid filled bushing including a hollow axial conductor and an expansion chamber for the liquid, said expansion chamber including a cap having a shoulder and a smooth cylindrical surface surrounding and spaced from the conductor, a ring threaded onto the conductor and sealed to the cap, an elastic seal secured to the ring between the conductor and the cylindrical surface of the cap, and a compression spring between the seal and said shoulder.

2. A liquid filled bushing including a hollow insulating wall, an axial conductor and an expansion chamber for the liquid, said expansion chamber including a base secured to an end of said wall, a nut threaded on said conductor within the expansion chamber, spring means between said nut and said base, said expansion chamber also including a transparent wall and a cap surrounding said conductor, a ring threaded onto the conductor and sealed to the cap, a sliding seal between said cap and conductor, and a compression spring spreading the seal into tight contact with the cap and conductor and pressing said cap onto the wall of the expansion chamber. 1

3. A liquid filled bushing including. a hollow insulating wall, an axial conductor and an expansion chamber for the liquid, said expansion chamber including a base secured to an end of said wall, a nut threaded on said conductor, spring means between said nut and said base, said expansion chamber also including a transparent wall and a cap surrounding said conductor, a ring threaded onto the conductor and sealed to the cap, a sliding seal between said cap and conductor, and a terminal enclosing the end of the conductor and sealed to said ring.

EUGENE D. EBY. 

